Manufacture of zinc oxid



.l. A. SINGMASTER, F. G. BREYER A ND E. H. BUNCE.

MANUFACTURE 0F ZINC OXID.

APPLICATION FILED IuLY 22.1919.

Patented Nov. 18, 191

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J. A. SINGMASTER, F. G. BREYER AND E. H. BUNCE.

MANUFACTURE 0F ZINC OXID'I APPLlcATloN HLED JULY 22.1919.

1 ,322, 1 42 Patented Nov. 18, 1919.

3 SHEETS-SHEET 2.

INVENTORS TYMK G IB gom A. SwlgAr BY M H Mu ATTORNEYS J. A. SINGIVIASTER, F. G. BREYER ANDV E. H. BUNCE.

MANUFACTURE 0F ZINC-OXID.

APPLICATloN man JULY 22,1919.

1,322, 142. Patented N0v.18, 1919 ATTORN EYS tion.

STATES PATENT Aonirica.-

.TAMES A. sINGMAsrEE, or NEW YORK, N. Y., AND FRANK c. BaEYEn AND EARL n. BUNcE, oE PALNEnroN, PENNSYLVANIA, AssIGNons rro THE NEW JERSEY ziNc comPANY, or NEW Yonx, N. Y., A oonronArIvoN or NEW JEnsEY.

VinANmAo'rURE or zINc ox'in.

Bpecication of Letters Patent.

' Application mea Juiyaa, 191e. semi No. 312,567

To all 'whom t may concern:

v Be it known that we, J AMES A. SINGMASTER, residing at New York city, county and State of New York, 'FRANK G. BREYER and EARL .5 H. Burro-E, both residing at Palmerten,

county of Carbon, State of Pennsylvania,

have invented certain new anduseful I mprovements in the Manufacture of Zinc AGrid, (Case E;) and we do hereby declare 110 the following to he a full, clear and exact 15 of zinc oXid or leaded. zinc oxid by the Wetherill process, and has for its objects the provision of an improved method of producing zinc oxid, or leaded zinc oxid, by the Wetherill process, in a continuous opera- Zinc oxid and leaded zinc oxid are principally produced in commercial practice by the so-called `Wetherill process. By the eX- pression Wetherill process, as we have usedthe saine herein, is to be understood the furnacing step of the process for producing zinc oxid, or leaded zinc oxid, as a tinished commercial product, or as a zinc oxid (or zinc-lead) concentrate, or in any other form, in which a charge of the zinkiferous (or zinkifferous and plumbiferouslmaterial miXed with a reducing agent and spread on an ignited bedof fuel is subjected to a combustion supporting blast or draft and 85 brought to a sufficiently high temperature vto reduce the compounds lof zinc and volatilize the reduced metal (and to reduce and (or) volatilize the compounds of lead when present) without bringing the charge to a condition where it becomes impervious to the blast or draft; the entire charge being supported on a furnaceV hearth or grate designed to hold it without letting any consid- 'arable' part drop through, and the workedoff material .being discharged as aclinker vor sinter. The furnacing step is independ ent of the subsequent treatment of the laden 'furnace gases and of the oollectionofthe zinc oxid or leaded -zinc oxid.

-In the commercial production l (including leaded'aincoxid) `hy means of the Wetherill process, it `has heretofore .been

f described furnace operation is attended with customary to firstcharge uponthe perfofinely-divided zinkiferous (or zinkiferous and plumbiferous) material, such as zinc silicate, roasted zinc blendes, roasted socalled mixed sulids of zinc and lead, spelter-retort residues, or other reducible zinc-containing (or zinc and lead containing) material at the disposal of the operator. The forced air draft is continued, and,-

whcn the familiar ames of greenish tint,

- Patented Nov. 18, 1919..

known as zinc candles, begin to make their appearancev above the upper surface of the charge, indicating that the `reduction and Volatilization of the zinc and its oxidation to the form of fume is well under way, the products of combustion carrying the zinc oxid fume and other volatilized metallic compounds are conveyed through the customary cooling fiues, etc., to the bag-room wherein, in aV cooled condition, they filter through the bags and pass oil' into the atmosphere, leaving the fume collected in the interior of the bags, from which it is removed at con- 'l venient intervals. The furnace operation is continued until the production of fume therefrom in appreciable quantity ceases,

whereupon the 'residual charge, which is, to aJarge eXtent,..-..sintered togetherq is broken up by long-handled rabbles and pried up and lifted or scraped out through the furnace doors into a receiving pit, or the like,

preparatory to the starting of a new operation. y The coal or other carbonaceous material .of the charge serves uthe two-fold purpose -of furnishing a reducing agent for effecting the reduction of the 'zinkiferous, or zinkiferous and plumbifemus, material of' thev charge and of furnishing, by combustion, l tliegnecessary ydegree of heat to bring. these :materials to the reducing temperature charvf: ajc'teistic 'of the process.

As" thus ordinarily practised, the above ima'V ciency. Prominent among these defects is the inevitable tendency to the formation of Il a fairly coarse grade. -SeriousY diiculties l Y i x 4but in spite of the pa blow-holes or craters at various regions of the charge. These blow-holes represent severally the paths of least' resistance for the blast in its passage through vthe charge and to the extent to which they develo in the progress of the operation the inter ere with the uniform distribution of the air in its upward passage and produce hot spots representlng excessive temperatures as compared with other regions of the charge. From time to time, the Workmen endeavor to eliminate these blow holes or hot spots, as far' as is` feasible, by rabbling the upper surface of the charge, thereby filling in the blow holes or breakin up their continuity;

lliative eiectof these expediente (which, moreover, consume considerable of the workmans time and attention) it is im y ible to obtain uniform worklng conditions throughout the entire extent of the charge; so` that there is not only waste of fuel, and the production'locally of higher temperatures than is de-` sirable, but the residues taken from the furnace at the'termination of the operation contain notable percentages of zinc. The zinc contained in these residues cannot ordinarily be recovered commerciall and, when the residues are employed in t eV manufacture of spiegeleisen or for the recovery of their lead orother values, the presence of the residual zinc is objectionable, for the reason that, when volatilized and oxidized in the furnace, it interferes to a greater or less extent Vwith the normal furnace operation and tends to collect in and obstruct the furnace flues.

A further defect of the above described furnace practice is that the forced draft, which is employed under relatively considerable pressure, tends to project into the free space above the charge more or less dust, particularly in the 'on of the blow-holes referred to, and this usting is further aggravated by the rabbling operations; conseuently, in addition to the metallic'fume, t e products of combustion carry with them from the furnace a notable proportion of dust in the form of fine particles of unreduced ore, carbon, ash, and the like, which tend to contaminate the flnne proper` and damage its color and marketability.

There are, furthermore, certain requirements of the practice of the Wetherill process as hereto ore conducted which ham the operator" in the'selection of the (page: Yand size bothof the'coeal and of the t'herous materia emp oy in making' up e charge. Thus, the uirement that the charge s hall be suicient y permeable for the Y passageofthe air neceitates the useof a mixture of coal and zinkiferous material of i charge can consistof such extremely finelydivided materials as flotation concentrates, zinc precipitates, flue-dust containing zinc, or the like.

The aforementioned defects and difficulties of the heretofore customary commercial Y tion in the prior customary practice of the Wetherill process are described in detail in the aforementioned' application.

In commercial practice, the furnace in which the Wetherill process is carried out has heretofore been generally constructed as a block containing several grate units. Thus, it is customary to build the )furnace or block with four if) twelve grate units, each of which may, for example, be about four feet wide and about ten feet long. These grate units may be arranged side by side, or half of the unitsmay be arranged side by side and the two?v halves arranged 'back to back. The purpose of this arrangement is to get relative continuity of action in the treatment of charges that individually are worked intermittently. Thus, while the operation of the furnace orblock may, for practical purposes, be considered more or less continuous, the operation with respect to any individual grate -unit is intermittent.

One of us, James A. Singmaster, has described and claimed in U. S. Letters Patent Nos. 1,112,853 and 1,112,854, patented Oct. 6, 1914, a process and apparatus for producing zinc oxid b the Wetherill processin which the ignlted charge is advanced through a suitable combustion zone in a continuous manner. One of the diiculties encount/ered in attempting to advance through Y a combustion zone a charge of finely-divided materials, such asthe heretofore customary Wetherill process charge, supported on a movable perforated grate, is that of providing' a seal at thesides of the charge.V The relative motion between the side walls of the combustion -zone and the moving charge provides a very susceptible region for the air blast to break through the charge, and

tiona'ry furnaceY walls with which -it'directly contacts. In -lthe aforementioned Letters Patent this diiiculty is avoided by supporting the charge, during its movement through the combustion zone, on grate sections so f arranged that the moving charge' is not in contact with any stationary element, the

p. grate sections themselves being designed to charge through a suitable combustionzone by supplying to the moving furnace hearth either or both the layer 'of bed fuel and the working charge in the form of briquets. The present invention thus contemplates advancing through a suitable combustion zone a working charge containing a briqueted mixture of zinkiferous, orplumbiferous-zinkiferous, material and a reducing agent spread on an ignited layer of bed fuel, also preferably in the form of briquets, and simultaneously passing a combustion supporting gas into the charge.

n our preferred practice, the Working charge, in ,the form of briquets made up of a mixture of zinkiferous material, or plumbiferous-zinkiferous material, and an appropriate reducing agent, is spread upon a Well ignited layerv of bed fuel also in the form of briquets, and the entire charge supported on a perforated furnace hearth, is advanced through a suitable combustion zone or chamber. The fuel briquets may, if desired, contain such a percentage of the zinkiferous or plumbiferouszinkiferous material as will not interfere with their normal function.

The bed fuel briquets may be prepared by` compressing nely divided \coal, together with a suitable binder, such, for example, as

the concentrated Waste sulite liquor of the sulte'pa er pulp industry. Various forms and gra es of Acarbonaceous material are available for the bed fuel briquets. Thus,

Y for example, anthracite coal belovv the No. 3

buckwheat Size, such as No. 4 buckwheat,

collier Wasliin dirt coal dust coal as Well as coke breeze, may be utilized in' the production of the bed fuel briquets. The bed fuel briquets are of such size and shape as to materially reduce the resistance to the combustion supportingv gas, and nevertheless .to supply vsu'cha substantially uniform subof such shape that they` roll or tumble easily over one another. Thus, we have `found the lso-called pillow block, eggette, roundedpillow block, over-stuffed pillow, and similar shapes well suited to the purposes of the invention. Y y

While the working charge consisting'of a mixture of zinkiferous, or zinkiferous and plumbiferous, material and an appropriate reducing agent may be supplied to the ignited layer of bed fuel briquets in an unbriqueted form, We prefer to briquet the Working charge because of the many attendant advantages. Furthermore, we Wish it to be understood that the zinkiferous, or zinkiferous andl lumbiferous, material may be briqueted a one, Without briqueting the reducing agent, or the reducing agent may be briqueted alone without briquetin' the zinkiferous, or zinkiferous and plumbierous, material, or the reducing agent and the zinkiferous, or zinkiferous and plumbiferous, material may be separately briqueted. However, our preferred practice is to briquet a mixture ofthe zinkiferous, or zinkiferous and plumbiferous, material and the reducing The reducing agent of the Working charge may be of any suitable lrind, and While We now prefer to employ carbonaceous material as the reducing agent, it will be understood by those skilled in the art that reducing agents other than carbonaceous materials are available for the purposes of the invention. One of the advantages of employing a briqueted ,reducing agent in any of the forms hereinblefore described is that it permits the use of carbonaceous materials of cheaper grades and finer mesh, such as anthracite coal of finer mesh than No. 3 buckwheat, colliery Washings, dust coal, coke breeze and the like.

The bed fuel 4briquets and the Working charge briquets may befprepared in any appropriate manner. We have found the procedure described in the aforementioned application of FrankI G. Breyer, .l ames A. Slngmaster andv Albert E. Hall, Serial No. 270,179, for preparing similar fuel and Working charge briquets Well adapted for the purposes of our present invention. This procedure involves generally the steps of mixing the material to be briqueted with a suitable binder, such as concentrated Waste sulfite liquor of 30 Baume, molding the mixture into briquets of the desired size and shape, and drying or baking the briquets at a temperature of approximately 200 C., so as to impart to them the desirable amount of resistance to crumbling and breaking so that they maybe freely subjected to the rough handling incident to storing them, conveyingl them to the furnace, and incident to vchargin' them into the furnace either by hand or .ot erwise. In the case of-the briqueted zinkiferous, or zinkiferous and plumbiferous, material, it is also desirable that the briquets possess such resistance to '50 have represented a p Fil crumbling and breaking as to substantially maintain their form during the entire furnacing operation, so that they are for the greater part discharged from the furnace in substantially their original physical form.

The remainl novel features of the invention can bengest ex lained by reference to the accompanying rawings, 1n which- Figure 1 is a sectional elevation of an improved furnace structure practically adapted or the practice of the invention; `ig. 2 is a side elevation of `the same; Fig. 3 is a top plan of the furnace; Figs. 4, 5 and 6 vare sectional views taken-on the section lines a sectional View of the water-cooled leveler for the bri ueted working charge, and Fig. 8 is a detai view of the perforated furnace hearth.

The furnace illustrated in the drawings has a movable or traveling hearth 10 in the form of a continuous belt or conveyer. The

furnace hearth may advantageously be of the general design used 1n mechanical stokers. As thus constructed, the hearth is made up of a plurality of metallic grate sections secured at their ends to sprocket chains 11. Each grate section is composed of a rigid frame piece havin a dove-tailed web .10 on which are strung or eyed the relatively narrow members 12. The members 12 while mechanically contacting with one another permit the passage of the combustion supporting dgas therebetween. The spaces between a jacent grate sections and between adjacent members 12 of each grate section rovide erforations orsmall passages uniormly istributed over the entire area of the hearth.

The two sprocket chains 11 coperate with --"4'5 wormreduction drives 17 and 18, beveled gears 19 and 20 and worm reduction drives 21 .and 22, respectively, to a common shaft 23. The shaft 23 may be driven from any suitable power sourci and to this end we operatively connected to the source of power,

such, for example, as an electric motor. By

this arrangement the shafts and 16, at

apposite ends of the furnace, ar'e driven at "55 e same speed, and the furnace hearth 10V is thereby positively driven by the co verating sprocket wheels at each end of the furnace. n l

The furnace housin -is constructed of fire 80 :brick in substantially t e usualmanner, with a casing of red brick on the outside. Thebrick work of the furnace structure, and in particular, the` arches and vskewbacks, are

eldin position'by vertical buckstays 25 and :at vtransverse tie-rods 26. The buckstays 25are- 4 4, 5 5 and 6 6, respectively; Fig. 7 is ley 24, adapted to bev 34 has an oitake 42. The throughY the oiftakes 41 'an preferably pivoted at their lower ends to anchor plates 27, referably embedded in concrete. Relative y heavy coil springs 28 are associated with the tie-rods 26, for forcing coperating pairs of buckstays on opposite sides of the furnace structure toward one another, thereby maintaining the buck. stays firmly pressed against the skewback plates 29.

The skewback lates 29 are L-shaped, as will be seen by re erence to Figs. 4 and 6 of the drawings, and are 'arranged to support the skewbacks 30. The furnace arches are supported by the skewbacks 30 in the usual manner, as will be more particularly pointed out hereinafter. It will be observed by reference to Figs. 4 and 6 of the drawings, that the buckstays 25 contact only with the skewback plates 29, and are thus separated by a small space from the side wall of the brick work structure. By this arrangement the tie rods 26 and coperating s rings 28 serve to force each coperating pa1r of buckstays `l firmly against the s kewback plates 29, ,and thus any shrinkage in the brick work structure of the' furnace arch, as the furnace dries out, is taken care of and the danger of the arch falling in is practically eliminated. The pivot mounting of the buckstays 25 at their lower ends rmits the necessary movement of the buclktays aboutthis pivot to compensate for shrinkage or expansion of the furnace arch.

i The interior of the furnace housing is divided into a series of chambers by suspended arches. Thus, an ignition or fuel combustion chamber 31 is provided at the charging end of the furnace by the suspended arches 32 and 33. An ore combustion chamber 34 is provided between the suspended arches 35 and 36. The Varches 33 and 35 are suitably spaced in order to accommodate the charging devices for the briqueted working charge, as will be fully described here-` inafter. The fume-emitting or oXid-making chamber 79 of the furnace is located between the suspended arches 36 and 37.

for conducting away from the fume-emitzone the eiiluent produced therein as the result of the o ration. The off-takes 38, 39 and 40 may Y connected to separate fume-collecting devices, or may communlcate with a common flue and fume-collecting device. The ignition chamber 31 .has an off-take 41, and the ore combustion chamber ases passing 42 may wasted or subjected to any pro r treatment.

At the discharge end of t e furnace a chamber 43 is rovded between the suspendedarch 37 an the arch 37'. On one side of the chamber 43 there is an observation door 44, while on the other side there is a sliding door 45. These doors are Yprovided as. a 180 means of easy access to the rear sprockets 14.

Observation doors 46 are provided at ap-4 propriate intervals lon each side of the furnace opening directly into the combustion chambers or zones thereof.

The suspended arches 32, 33, 36 and 37 are held in position in substantially the saine manner. Each of these arches is built of a plurality of rectangular fire brick. Rods 47 are embedded in these rectangular lire bricks and passing upwardly through the furnace arch and roof are secured in place by being bolted to transverse beams 48'. The sector-shaped spaces-between the upper surface of these rectangular lire bricks and the curved lower surface of the furnace arch are filled in with fire bricks so as to form the desired partition between the various cham bers of the furnace.

rlhe furnace arch or roof 49 is constructed of fire brick in the usual manner and is supported in position by the skewbacks 30, as will be well understood in the art. A cinder fill 50 may be placed on-top of the arch 49. Along each side wall of the furnace, just above the working surface \of the traveling grate 10, carborundum bricks 51 are used to prevent fusion between the charge and the side walls of the furnace.

A hopper 52 is arranged at the front or charging end of the furnace for feeding the briqueted bed fuel on to the traveling glggrate.l

A gate or charge leveler 53 is associated with the hopper and is adapted to be raised or lowered by means of a wheel 54, and cooperating mechanism. By thus raising or lowering the gate 53, the depth of charge fed on to the traveling grate 10 may be regulated to the desired amount.V

A hopper 55 is arranged to discharge into the space between the suspended arch 33 and the arch 35. A water-cooled gate or leveler 56 is arranged behind the hopper 55 for leveling the charge fed on to' the traveling grate by the hopper. 'lhe gate 56, as will be seen by referenceto Fig. 7 of the drawings, com rises a'hollow shell having transverse ba es 57 for imparting to the cooling medium flowing therethrough a circuitous path. rlhis cooling medium, such, for example, as water, may be supplied to the interior of the-hollow shell by an inlet pipe 58, and withdrawn by an' outlet pipe 59. The gate 56 is suspended from the top of the furnace structure -by vertical rods 60 and may be vertically adjusted with respect to the moving grate by means of the nuts 61.

As hereinbefore explained, the drive for the traveling grate is connected so that the grate is driven both from the front and rear through the main powershaft. The return `grate is supportedon riding bars 62 fask tened to the side plates 63 of 'the furnace.

The working door of the furnace is supported on a suitable foundation 64, preferdrawings.

'ranged in each of the. air` compartments, and

Abeneath the upper or working surface of the traveling grate. Four air boxes 67 extend transversely of the furnace structure, at appropriate intervals between the front and rear thereof, and serve to admit the necessary blast of combustion supported gas beneath the perforated grate 10. '.lhe space between adjacent air boxes 67 is divided into two compartments by means of the vertical partitions 68. By this arrangement it vwill be observed that eight air chambers or compartments are provided beneath the perforated traveling grate 10.. Wear plates 67' 5 and 68 are preferably mounted on the tops of the air boxes 6.7 and partitions 68, re-P spectively, to serve as bearinoplates for such ortions of the traveling Igrate as contact t erewith. The first air compartment at the front or chargin end of the furnace is closed on the outsi e by a sheet metal wall 69, and a similar wall 70 closes the last. air compartment at'the rear or discharge end o-f the furnace.

Each of the air boxes 67 extends exteriorly of the furnace at one side, as will be seen by reference to Figs. 2, 3 and 4 of the Each air box is connected exteriorl of the furnace by a vertical pipe 71 with `tliie main air conduit 72. Each of the pipes 71 is provided with aV slide valve '73,` for regulating the air supply to its air box. Both of the transverse walls of eachfair box 67 are provided withtwyers or openin s 74. A slide damper 75, terminating in a andle 76 exteriorly of the air box, is provided for each series of twyers 74. Y By moving thehandles 76 in or out, the area of the twyers or openings 74 can be adjusted, and in this manner the adjustment of the blast secured.' llt will be observed that while each air box serves to supply the combustion supporting gas to two air compartments, the amount ofgas supplied to 'each compartment may be regulated by manipulation of the appropriate'slide damper 75.

A trough 77 forI water is preferably ar-V a, pipe y78 may connect with for conducting water thereto.

ln practisin the method of oui` present invention in t e furnace illustrated in the accompanying drawings, the fuel briquets the' troughs may beraised or lowered to any height deiie isa

are fed in at the front end of the grate Y sired. From this point the fuel briquets travel into the fuel combustion chamber 31 and are there ignited by the high temperature maintained in this chamber. The gases from the fuel combustion chamber are carried oil' through the stack 41.

At the rear of the fuel combustion chamber, just back of the suspended arch 33, the

briqueted working charge is fed on to the ignited fuel briquets through the hopper 55. The depth of the briqueted working charge is regulated by the gate 56, which may be set at any desired height. As previously explained, this gate is cooled by means of circulating water. The briqueted working charge thus spread on the ignited fuelbriuets is advanced into what we have called t e ore combustion chamber 34, in which the charge is brought up to the reducing temperature. The stack 42 is provided so that, if desirable, the eiiiuent made in this chamber may be recovered separately from that produced in the main oxid-making cham-- ber 79.

The briqueted charge now passes under the suspended arch 36 into the main effluent or OXid-making chamber 79, in which the active reduction of the charge takes place. The blow or blast in this chamber is so regulated that complete reduction takes place by the time the charge has traveled to the rear of the chamber. From the oxid-making chamber the three off-takes 38, 39 and 40 conduct the effluent to the oxid drum, as will be well understood in the art. Each of the off-takes 42, 38, 39 and/40, is provided with a slide damper42, 38', 39 and 40', respectively, for regulating the flow of the efuent, so as to help control the temperature at all points of the chamber 79. A' trailing door or gate 80 is operativelyv mounted on the suspended arch 37 for preventing the passage underneath the arch and into the chamber 79 qf currents or drafts of air.

From the main oXid-making chamber 79,

. the worked ofi' briquets pass underneath the suspended arch 37 into the rear chamber 43. This chamber is also provided with a stack 82, for balancing the draft.l between the rear chamber and the oxid making chamber. As the-grate sections ,pass over the rear sprockets-14, the worked-off charge,

consisting -of a light coal clinker and r the chamber 43 normally closed. Wlnfn a certain amount of residue banksup a ainst this door 81 it swin open to permit the discharge of the resigde down the chute 65.

The traveling furnace hearth moves at a very slow speed, a few feet per hour. The

speed of the hearth will be determined by the dimensions of the fume-emitting zone, the character andquantity of zinkiferous material charged and other considerations, which will be understood by those skilled in the art. We have found a temperature of approximately 1100 to 1250o C. well suited for the fume-emitting or oxid-making chamber or zone, when using the well known Franklin furnace zinc oxid ores, and at this temperature the briqueted working charge can ordinarily be satisfactorily worked-oil or depleted of its zinkiferous content in from two and one-half to three and one-half hours, when operating with a furnace whose oxidmaking chamber 79 is about eighteen feet 1n length and with a grate speed of about seven feet per hour.

lnthe customary commercial practice of the Wetherill process, the total carbonaceous material in the entire charge, including the bed fuel and the working charge mixture, is several times greater than the theoretical amount required to reduce the zinkiferous material in the charge. It has heretofore been the general practice to lace the greater proportion of the total car onaceous material of the charge in the working charge mixture'. For example, when'operating with the well known Franklin furnace zinc oxid ores, it is customary to place from about 15 to 25 per cent. of the total carbonaceous material of the entire charge in the bed fuel, while the remaining 85 to 7 5 per cent. of the total carbonaceous material ismixed with the ore to form the working charge. In general terms, the layer of bed fuel is approximately one inch inl depth or thickness, while the workingcharge mixture is spread over the ignited bed fuel in a layer from about five to seven inches in depth or thickness.

A very decided improvement in the eficiency of the Wetherill process can be secured by lacing the greater proportion of the total uel of the charge in the form of briquets' in the bed fuel, rather than in the working charge as has heretofore been customary. vThis improvement'in the heretofore customary practice of the Wetherill process is described and claimed in an application for Letters Patent of the United States of Frank G. Breyer, Albert-E. Hall and George R. Waltz, Serial No'. 310,439, filed July 12, 1919. When a Very considerable proportion of the carbonaceous or other combustible material of the entire charge is thus withdrawn from the working charge and placed inthe bed fuel in the form of briquets, the residual charge consists of a relatively thin clinkered ash, resulting from the combustion of the bed fuel briquets, and the worked-off metalliferous material. When the Zinkiferous material has been briqueted and spread on the ignited bed fuel briquets, the worked-off ore briquets .are discharged in substantially their original physical form, 13

o ore briquets is relatively small, and such worked-ofi' briquets may on this account be vadded as a binder.

very advantageously employed in subse uent smelting operations for the recovery t erefrom of further metallic values, as will be more fully described hereinafter. Accordingly, in view of the attendant advantages, it is our preferred practice in carrying out the present invention to place the greater part of the total carbonaceous or combustible material of the entire charge in the bed fuel briquets, and We have secured excellent results by placing from about 7 5 to about 85% of the total combustible material of the entire charge in the bed fuel briquets.

As a typical instance of the practice of the inventlon, We will now describe a particular operation in which both fuelbriquets and a briqueted Working vcharge were used. Eighty-ve (85) per cent. of the total coal of the entire charge was carried in the bed v fuel briquets, leaving fifteen (15) per cent,

of the total coal for mixture with the zinkiferous material in the working charge. The fuel briquets were made up of dust -coal With three (3) per cent. concentrated Waste sulte liquor binder. rlhe briqueted Working charge'consisted of a mixture of ninety (90) per cent. Franklin furnace zinc oxid ore and ten (10) per cent. dust coal, to which three (3) per cent. Waste sulite liquor was Both the ore and fuel briquets 4WereV of the rounded pillow block ty e. y

he levelers or gates 53 and 56 lof the accompanyingdravvings Were set to deliver a layer of bed fuel six inches deep and a three inch layer of the briqueted Working charge.

' in the foregoing' operation, We secured very satisfactory results by holding the fuel ignition chamber 31 at the minimum temperature for uniform ignition, thatis, from about 800 to 950@ the ore ignition' chamber Si at a temperature Where a lightzinc ila-me is visible, for example, from 1000 to 1050o C., and the oxid-making chamber 7 9,A

at a `lplniforni temperature of from 1100" to 1250 C., since' at this temperature reduction is active, and with the usual working mixtures only incipient fusion of the briqueted'vvorking charge takes place.

No bars or rakes need be used, nor need the charge be disturbed in any, manner in practising the method of ourpresent ine; yention. rihe only labor necessaryv consistsk in feeding the briquets to the furnace and carting away the clinker and worked-0E briquets discharged into the-hoppers or cars provided therefor. -There is, furthermore, no blow-h'ole trouble, and no sticking of the charge to the side wallsfand no loss of blow at the side walls.' The briquets feed uniformly and the ignition of both fuel and working charge briquets is veryuniform.A

The clinker, consisting of a relatively thin layer of coal 4ash and burned-out brlquets, discharges readily and no labor is attendant upon the discharging operation.

I The oXid-made in accordance with ourinvention is decidedly superior to that made from charges of the same ore on the customary. oxid furnace blocks. It' is partie' i ularly free from any 'tor specks and very bright. The recoveries of zincl from the Working charge' are remarkably high, and l We have found by thepracticeof our invention, that it is possible to secure recoveries better than ninety percent., as indicated by the clinker analysis.

When, as in the preferred embodiment Y of the invention, the zinkiferous, or zinkiferous and plumbiferous, material of the- Workin charge is supplied to the furnace hearth 1n the formof briquets, the Workedo ore briquets retain for the most part their original shape with only incipient fusion. Some of the Working charge briquets will almost inevitably become broken or crushed "in the preliminary handling and furnacing operation, but these briquets for the greater partretain their original physical form. After the'furnacing operation, these briquets are remarkably hard and almost coke-like in their physical characteristics, and are readily separated from the clinkered coal .A

ash of the bed fuel briquets.

This capability of readily separating the Worked-oli' ore briquets from the ash of the fuelv briquets is of especial advantage when the Worked-olit metalliferous briquets are to be subjected to further treatment for the 4recovery of valuable metals not Volatilizable by the Wetherill process. ilVhei-e the Working charge briquets consist of a mixture of zinlriferous or zinkiferous and plumbiferous material and carbonaceous reducing agent, the ,worked-0E briquets willcontain, in addition to the worked-O' zinkiferous, or zinkiferous and plumbiferous material, the ash from the consumed 'carbonaceous reducing agent as Well as the unconsumed portion of the reducing agent. The ash is composed principally of silica and alumina,

'and is generally objectionable inany subsequent treatment of the Worked-od ore briquets. rihus, for example, in. those instances in which thejWorked-o' ore briquets are smelted in a'blast furnace for the .production of spiegeleisen a certain amount of iuxing agents is necessary for slagging o the ash present in the Worked-off ore briquets, and when this amount of ash is relatively large an objectionably large amount of uxing agent is required, with the resul ,tant production of an objectionably large amount of slag. By placing approximately 85% of' the total carbonaceous material of the entire charge in the bed fuel briquets, the main bulk, for example, around eightyfive (85) per cent., of the ash of the total carbonaceous material of the charge is in the clinker resulting from the combustion furnaces. In addition to retaining their.

original form, these briquets are moreover of a porous character, due to the removal of the zinc, or zinc and lead, therefrom, and this porous property of the worked-olf briquets is also of advantage in tlieir subsequent treatment.

A very accurate and uniform control of the temperature throughout the entire furnace, and hence during the entire furnacing operation of the charge, is secured by the practice of the invention. Thus, the temperature of the various chambers or zones of the furnace can be accurately regulated and controlled .by appropriately adjusting the slide dampers 73 of the various air compartments, and the desired operating temperaf tures are easily maintained throughout the entire furnace. This uniformity of the temperature conditions is attended by ractically uniform Working conditions of t e desired character throu hout the furnace, and results in the production of a uniform product of improved quality as well asin increased output. The furnacing operation is substantially automatic, and requires only casual attention, thereby effecting a great saving in labor over that required .in the' operation of the present day types of oxid furnaces. The combustion of the bed fuel is substantially complete, so-that practically the full caloric value of the fuel is effectively utilized, thereby enabling a saving in the amount of fuel required as compared with that necessary in Working with the heretofore customary types of oxid furnaces.. The worked-olf briquets are, in our preferred practice, onl slightly contaminated with ash and the li e, and on this account, as Well as on account of their ph sical form and properties these worked-olf riquets are Well adapted for subsequent smelting operations.

We claim: l

1. The process of producing zinc oxid or lleaded zinc-oxid which comprises advancing through a suitable combustion zone a Working charge containing a briqueted mixture of zinklferous or zinkiferous and plumbiferous material and a. reducing agent spread on an ignited layer of bedrfuel in the form 'of briquets and simultaneously passing a combustion supporting gas into the charge, and removing the resulting eluent5 substantially as described.

2. The process of producing zinc oxid or leaded zinc oxid which comprises advancing through a suitable combustion zone a Working charge containing a mixture of briqueted zinkiferous or zinkiferous and plumbiferous material and a reducing agent spread on an ignited layer of bed fuel in the form of briquets and simultaneously passing a combustion supporting as into the charge, and removing the resu ting eiuent; substantially as described.

3. The process of produci zinc oxid or leaded zinc oxid which comprises advancing through a suitable combustion zone a Working charge containing briqueted zinkiferous or zinlriferous and plumbiferous material spread on an ignited layer of bed fuel in the form of briquets and simultaneously passing a combustion supporting gas into the charge, and removing the resulting eiuent; substantially as described.

4. The process of producing zinc oxid or leaded zinc oxid which comprises advancing through a suitable combustion zone a Working charge containing a mixture of zinkiferous or zinkiferous and plumbiferous material and a briqueted reducing agent spread on an ignited layer of bed fuel in the form of briquets and simultaneously passing a combustion supporting gas into the charge, and removing the resulting effluent; substantially as described.

5. The process of producing zinc oxid or leaded zinc oxid which comprises advancing through a suitable combustion zone a Working charge containing a mixture of zinkiferous or zinkiferous and plumbiferous material and a reducing agent spread on an ignited layer of bed fuel in the form of briquets and simultaneously passing a combustion supporting gas into tile charge, and removing the resulting eluent; substantially as described.

6. The process of producing'zinc oxid or leaded zinc oxid which comprises advancing through a suitable combustion zone a working charge containing zinkiferous or zinkiferous and plumbiferous material spread on an ignited layer of bed fuel in the form of briquets and simultaneously passing a combustion supporting gas into the charge, and

leaded zinc oxid which comprises advancing through a suitable combustion zone a working charge containing a briqueted mixture of zinkiferous or zinkiferous and'plumbiferrous material and a reducing agent Aspread X30' on au ignited layer of bed fuel and simultaneously assing a combustion supporting gas into t e charge, and removing the resulting eiiiuent; substantially as described.

8. The process of producing zinc oxd or leaded zinc oxid which comprises advancing through a suitable combustion zone a working charge containing a mixture of briqueted zinkiferous or zinkifei'ous and pluinbiferous material and a reducing agent spread on an ignited layer of bed fuel and simultaneously passing a combustion supporting gas into the charge, and removing the resulting eiiuent; substantially as described.

9. The process of producing zinc oxid or leaded zinc oxid Which comprises advancing through a suitable combustion zone a Working charge containing briqueted zinkiferous or zinlriferous and plumbiferous material spread on an ignited layer of bed fuel and simultaneously passing a combustionsupporting gas into the charge, and removing i the resulting effluent; substantially as described.

10. The process o f producing zinc oxid or leaded zinc oXid which comprisesy depositing u-pon a perforated hearth a layer of bed fuel in the form of briquets, igniting said layer of briquets, spreading thereon a Working charge containin a briqueted mixture of zinkiferous or zin riferous and plumbiferous material and a reducing agent, advancing said hearth and the charge supported thereon through a combustion zone and simultaneously passing a combustion supporting gas into the charge, and removingthe resultin eiiuent; substantially as described.

11. he process of producing zinc oxid or leaded zinc oxid which comprises depositing upon a perforated hearth a layer of lbed fuel' in the form of briquets, igniting said layer of` briquets, spreading thereon a working charge containing a mixture of briqueted zinkiferous or zinkiferous and plum'- 45 biferous material and a reducing agent, ad-

vancing said hearth and the charge supported thereon through a combustion zone and simultaneously assing a combustion supporting gas into t e charge, and removing the resulting eiiiuent; substantially as described.

12. The process of producing zinc oxid or leaded zinc oxid which comprises depositin upon a erforated hearth a layer of bed fue in the" orm of 'bri uets, igniting said layer of briquets, s prea ing thereon a working charge containing briqueted zinkiferous or zinkiferous and plumbiferous material advancing said hearth and the charge supported thereon through a combustion zone and simultaneously passing,v a combustion .supporting gas into the charge, and removing the resulting eiliuent; substantially as described.

- f .66 13; The process of producing zinc oxid or leaded zinc oxid which comprises depositing y upon a perforated hearth a layer of bed fuel in the form of briquets, igniting said layer of briquets, spreadin thereon a Working charge containing a mixture of zinkiferous or zinkiferous and plumbiferous material and abriqueted reducing agent, advancing saidv hearth and the charge supported thereon through a combustion zone and simultaneously passing a combustion supporting gas into the charge, and removing the resulting eluent; substantially as described.

14. The process of producing zinc oXid or leaded zinc oXid which comprises depositing upon a perforated hearth a layer of bed fuel in the forni of briquets, ignting said layer of briquets, spreading thereon a Working charge containing a mixture of zinkiferous or zinkiferous and plumbiferous mate- 85 rial and a reducing agent, advancing said hearth andthe 4charge supported thereon throu h av combustion zone and simultaneous y passing a combustion supportin gas into the charge, and removing the resu ting eiuent; substantially as described.

1f5. The process of reducing zinc oxid or leaded zinc oxid whic comprises depositing upon a erforated hearth a layer of bed fuel in the orm of briquets, igniting said layer of briquets, spreading thereon a vv'orking charge containing zinkiferous or zinkiferous and plumbiferous material, advancin said hearth and the charge supported t ereon through a com'bustion zone and simultavneously passing a combustion .supporting gas into-the charge, and removing the resulting effluent; substantially as described.

16. The process of producing zinc oXid or leaded zinc oxid which comprises depositing upon a perforated hearth a layer of bed fuel, igniting said la er of bed fuel, spreadin thereon a wor ing charge containing a riqueted mixture o zinkiferous ,or zinkiferous and plumbiferous material and a reducing agent, advancing said hearth and the charge supported thereon through a combustion zone and simultaneously passing a combustion supporting gas into the charge, and removin the resultin effluent; substantially as escribed.

17. he process of producing zinc oxid or leaded` zinc oxid'which comprises depositing upon a perforated hearth a layer of bed fuel, igniting said layer of fuel,` spreading thereon a working charge containing a mixture of briqueted zinkiferous or zinkiferous and plumbiferous material and Va reducing agent, advancing said hearth and the charge supported thereon through a combustion zone and simultaneously assing a combustion supporting s into t e charge, and removing the resu ting eiuent; substantially as described.

18. The process ofv producing zinc oxid` 130 or leaded zinc oxid which comprises depositing upon a perforated hearth a layer of bed fuel, igniting said layer of bed fuel, spreading thereon a Working charge containin briqueted zinkiferous or zinkiferous and p umbiferous material, advancing said' hearth and the charge supported thereon through a combustion zone and simultaneously passing a combustion supporting gas.. into the charge, and removing the resulting edluenir substantially as described.

19. 'lzhe process of producing zinc oXid or leaded zinc oXid which comprises depositing upon a furnace hearth a layer of bed fuel containing the greater part of the total l combustible materialof the 'entire charge in the form .of briquets, ignit'ing said layer of hed fuel, briquets, spreading thereon a Working charge containing a briqueted mixture of zinkiferous or zinkiferous and f plumbiferous material and a reducing agent,

advancing said hearth and the charge supported thereon through a combustion zone and simultaneously passing a combustion supporting gas into the charge, and removing the resulting eiiiuent; substantially as described.

20. The process of producing zinc oxid or leaded zinc oXid which comprises depositing upon a 'furnace hearth a layer of bed fuel containing the greater part of the total combustible material of the entire charge in the form of briquets, ignitinN said layer-of bed fuel briquets, spreading t ereon a Working charge conta'inlng a mixture o f briqueted zinkiferous or zinkiferous and plumbiferouso material and a reducing agent, advancing said hearth and the charge supported there- 0n through a combustion zone and simultaneously assing a combustion supporting gas into t e charge, and removin the resulting eluent; substantially as described 2l. The process of producing zinc oXid or leaded zinc oXid which comprises depositing upon a furnace hearth a layer of bed f fuel containing the greater part of the total combustiblemateri'al of the entire charge in the form of briquets, ignitin said layer of bed fuel briquets, spreading t ereon a Working char e containing briqueted zinkiferous or zinki erous and plumbiferous material, advancing said hearth and the chargesupported thereon through a combustion zone' and simultaneously assing Ia combustion supporting gas into t e charge, and removv ing Ythe resulting. eliuent; substantially as described.

22. The process of producing zinc oxid or leaded zinc ozcid which-comprises depositing upon a furnace hearth a layer of bed fuel containing the greater part of the' total vcombustible material of the'entire charge in the form of briquets, ignitin said layer of bed fuel briquets, spreadingt ereon a working charge containing a mixture of zinliif.- erous or zinkiferous and plumbiferous material and a briqueted reducing agent, advancing said hearth and the charge supported thereon through a combustion zone and simultaneously passing a combustion supporting gas into the charge, and removing the resulting effluent, substantiallyT as de'- scribed. v

23. The process of' producing zinc oXid or leaded zinc oxid which comprises depositing upon a furnace hearth a. layer of bed fuel containing the greater part'of the total combustible material of the entire charge the form of briquets, igniting said layer of bed fuel briquets, spreading thereon a Working charge mixture containing sinkiferous or zinkiferous and plumbiferous material and a reducing agent, advancing said hearth and the chargesupported thereon through a combustion zone and simultaneously passing a combustion supporting gas into the charge, and removing the resulting efliuent, substantially. as described.

24. The rocess o f producing zinc oxid or leaded zinc oXid which comprises deposit- -ing upon a furnace hearth a lay-er of bed fuel containing the greater part of the total combustible material of the entire charge in the form of briquets, ignitin said layer of bed fuel briquets, spreading thereon a working charge containing zinkiferous or Izinkiferous and plumbiferous material, ad-

vancing said hearth and the charge supported thereon through a combustion zone and simultaneously plassing a combustion supporting s into t e charge, and removing the resu ting effluent, substantiallyfa'sIA described.

25. In a process for produein zinc'oziid a metal-bearing material 'and- We aix our signa- 

